The focus of the program is on the mechanisms of heterogeneity of ventilation and perfusion in the lung. The program consists of five projects and three cores which address both intraregional and interregional mechanisms of heterogeneity. The projects deal either with ventilation or perfusion separately, the matching of the two as it affects gas exchange and influences on edema formation. The approach is multidisplinary, with investigators trained in medicine, physiology, anesthesiology, bioengineering, morphology, engineering, and radiology. It is the result of two decades of interest in pulmonary physiology and medicine and collaboration between the investigators. The program is designed to support other research, particular in ARDS and pulmonary vascular disease, which is proceeding at the University of Washington. The strengths of the program include the integration of many disciplines, the productivity of this group of investigators, and the adoption of new experimental approaches using imaging, morphological reconstruction, and fractal evaluation of heterogeneity.